Hydrorefining of low-temperature tar fractions



v. M. sTowE 2,983,666

HYDROREFINING oF Low-TEMPERATURE TAR FRACTIONS May 9, 1961 Filed Deo. 10, 195'? mEEwwt e mw m TO N NT. R ws/@m mM M l mw/y we nited States Patent O HYDROREFINING F 'LOW-TEMPERATURE TAR FRACTIONS Vernon M. Stowe, Caseyville Township, St. Clair County,

lll., assignor to Aluminum Company of America, Pittsburgh, Pa., a corporation of Pennsylvama Filed Dec. 10, 1957, Ser. No. 701,817

2 Claims. (Cl. 208-42) This invention is related to the treatment of low-temperature tar fractions with hydrogen to produce reiined hydrocarbon liquids and other valuable products. More particularly, it is directed to a method for the production of hydrocarbon liquids suitable for use as solvents by hydroretning fractions of tars produced by low-temperature carbonization of bituminous materials.

Peat, brown coal, lignite, sub-bituminous and bituminous coals are bituminous materials vwhich have been proposed as feedstocks for low-temperature carbonization processes to secure chars or cokes for use as fuel, and tars from which valuable products might be obtained. The present invention is directed to the utilization of such low-temperature tars and to the hydrogen-treatment of fractions thereof to produce refined hydrocarbon [liquids suitable for use as solvents.

The term hydroreningf as used4 herein, refers to the catalytic treatment of low-temperature tar vfractions comprising, at least in part, organic compounds containing combined heteroatorns such as sulfur, nitrogen, and oxygen, at high temperatures in the presence of hydrogen under medium pressure to produce ammoniacal compounds, hydrogen sulide, water and the corresponding hydrocarbons.. Saturation of olens generally accompanics the removal of the heteroatoms, and other reactions may incidentally occur such as cyclization, dehydrogenation and deaikylation.

The term low-temperature carbonization, as used is only partially aromatic, i.e. about 10-45 percent.

herein, refers to a process forfthe carbonization of bituminous materials at temperatures lower than about 1300 F. Representative of such a process is that described by V. F. Parry in U.S. Patent 2,773,018 and in Drying and Carbonizing Fine Coal in Entrained and Fluidized State, Bureau of MineslReport of Investigations 4954, U.S. Department of Interior, dated April 1953.

The term low-temperature tar, as used herein, refers to tars produced by low-temperature carbonization of peat, brown coal, lignite, sub-bituminous or bituminous coals. Such tars are generally oily, tarry organic masses ranging from viscous liquids to soft semi-solid materials at room temperature and may contain small quantities of char ash or other inert material, dissolved gases and water. i i

A typical analysis of low-temperature ta'r obtained by carbonization of Texas lignite at 946. F. utilizing the Parry process, supra, is shown n Table l below:

TABLE 1 Analysis of crude tar Ash, weight percent 0.35 Specic gravity, 60/60 F. 0.9867 Moisture, weight percent 2.9 C-I (quinoliue-insolubles), weight percent 1.41

2,983,666 Patented May 9, 1961 Distillation ASTM D20-52, dry basis, weight: percent: To 170 C. 2.2 170235 C. 18.4 235-270 C. 12.6 270-300 C. 12.8 300 C. to decomposition temperature 31.3 esidue at decomposition temperature oss Decomposition temperature, C. 329

Analysis of distillate, vol. percent:

Tar bases 4.3

Tar acids 23.9

Neutlrialdoil b ty 1 71.8

y rocar on pes Saturates 14 Olens 40 Aromatics 46 1 Method disclosed in article by G. U. Dinneen et al., Shale Oil Napthas: Analysis of Small Samples by Silica Gel Adolrrtgon Method,V Analytical Chemistry, vol, 19, p. 992

Low-temperature carbonization is generally favored for the production of large quantities of tar as compared to high-temperature processes,v thus permitting recovery of considerably greater amounts of tar oils. However, considerable dierences exist in the nature of the tars. High-temperature tars are almost completely aromatic and about percent consists of 3 to 7 ring aromatic compounds with molecular weights up to 400, the remainder `consisting of higher molecular weight carbonaceous compounds; in addition, the percentage of phenolic constituents is low, about 5 to l2 percent, but substantially all of these are low-boiling tar acids. Low-temperature tar It contains relatively large quantities of phenolic constituents, ranging from 20 to 45 percent of the tar; however, these are about evenly distributed in the valuable lowboiling phenolic 4range and in the higher boiling fraction.

The by-product recovery treatment of such tars may involve a distillation process to recover low-boiling oils from which tar acids are recovered. These phenolic constituents are usually a readily marketable commodity and constitute a definite enhancement to the value of the products obtainable from the process. 'Tar bases may also be extnacted from the distillate, although they are of less commercial signilicance. Heretofore, the: neutral oils remaining after such extraction have been considered generally only as .fuel oils because of the high content of sulfur and other heteroatoms; The pitch residue which constitutes a great percentage of the original tar, about 25 to 80 percent, has generally been considered of poor economic value, and used as a fuel or a briquetting binder.

lt is an object of this invention to provide a method for substantially complete utilization of low-temperature tar.

Another object is to provide a method for the treatment of low-temperature tar whereby refined hydrocarbon liquids and other valuable products are obtained.

`It is also an object to provide a method for the hydroreiinng of low-temperature tar fractions to produce hydrocarbon solvents substantially yfree from sulfur, nitrogen, oxygen and other undesirable impurities.

Further objects and advantages of the presentinvention will be evident from the attached drawing and following detailed specication.

In accordance with the present invention, a low-temperature tar fraction is catalytically treated with hydrogen sure between and 1000 p.s.i.g., a temperature bebetween 1000 and 6000 cubic feet per barrel of feed.

Preferably, the crude or whole tar is initially distilled to to recover phenolic oil Aand middle oil, and the phenolic oil is desirably processed to recover tar acids and tar bases, leaving a neutral oil., The middle oil is employed as the feed to the hydrorening reactor, and the neutral oil may `also be treated therein, either separately or in admixture with the middle oil. The residue from the distillation may be returnedto the carbonizer or treated in accordance with other proceses.

The term phenolic oil, as used herein, refers to a tar distillate relatively rich in valuable low-boiling phenolic components, such as phenol, cresols, xylenols and ethyl phenols. It is preferred to use about 235 C. as the end point for this distillate, although variations may be made dependent upon the icompounds desired in this fr-action.

The term middle oil, as used herein, refers to a tar distillate boiling above the phenolic oil range.

The term tar distillate, as used herein, refers to any distillate from low-temperature tars, and may encompass phenolic oil or middle oil, or both.

The term low-temperature tar fraction, as employed herein, refers to a distillate from low temperature tar, either whole or extracted, and may encompass middle oil, phenolic oil, oils obtained by caustic-washing of phenolic or middle oils, neutral oils obtained by extraction of phenolic or middle oils, and mixtures thereof.

For a more detailed description of the invention, reference is made to the accompanying drawing, which is a diagrammatic ow sheet illustrating an embodiment of the invention.

A low-temperature tar 2 is subjected to distillation or topping in a still 4 to recover phenolic oil 6 and middle oil 3, leaving residue 10. The middle oil 8 is subjected to hydrorefining in reactor 22, wherein it is treated with hydrogen-rich gas 24 to remove undesirable impurities, such as sulfur, nitrogen and oxygen, as well as to` saturate oletinic constituents. The resultants are liquid product 26 and off-gas 28 which is desirably processed in the hydrogen-purification plant 30 to recover hydrogen or hydrogen-rich gases which then may be recycled as the reactant gas 24.

The liquid product 26 is refined partially aromatic oil, substantially free from noxious impurities, which may be used as a solvent. The liquid product is preferably fractionated in the column 32 into several fractions and a relatively high-boiling residue 34, which may be recycled for further processing in the reactor 22.

The higher-boiling fractions from the column 32 may desirably be subjected to a further refining step, such as by treatment with 70 percent sulfuric acid or by ltration. i

The phenolic oil 6 is desirablyY subjected to a conventional treatment 12 to recover the tar bases 16, which treatment may be of the type utilizing dilute acid, and to a second treatment 14 to remove the tar. acids 18, such as by washing with caustic solution or solvents, leaving a low-boiling neutral oil 20.

The neutral oil 20 is conveniently processed in the reactor 22 in order to refine it to valuable solvents, separately or in admixt'ure with the middle oil, or it may be used without further treatment, if desired.

The residue is preferably subjected to a delayed coking operation such as is described in the copending application of M. B. Dell, Delayed Coking of Low- Temperature Tars, Serial No. 791,615, filed February 6, 1959.

Temperatures between about 800 F. and ll50 F are employed for the hydrogen treatment, the specific ternperatures depending upon the nature of the low-temperature fraction treated. Temperatures above 1150 F. tend to reduce the yieldof liquid product, whereasv tempera- 4 tures below 800 F. do not effect sufficient removal of the heteroatoms. Generally, it is preferred to use ternperatures between 900 :and 950 F. for neutral oil boiling below about 235 C., and temperatures between 950 and 1000 F. for middle oil.

The hydrorefining proceeds satisfactorily at total pressures between 100 and 1000 pounds per square inch gauge. Pressures above 1000 p.s.i.g. cause excessive cracking of the molecules and hydrogenation of the aro matic nuclei, while pressures below 100 p.s.i.g. result in increased deposits of carbonaceous materials on the catalyst. Generally, a pressure between 500 and 800 p.s.i.g. is preferred for treatment of both neutral oil and middle oil.

The liquid hourly spiacevelocity may be between 0.25 and 4.0 volumes per volume of catalyst per hour. Generally, lower space velocity rates decrease the liquid product yield, whereas higher rates do not provide sullicient purification of the feed. Preferably, a rate of between about 0.5 and 1.3 is employed for treatment of all tar fractions.

The hydrogen feed should be in excess of stoichiometric requirements and amounts less than this fail to provide `sufficient purification, and quantities above 6000 cubic feet per barrel become prohibitive both from cost and handling standpoints. Generally, about 3000 cubic feet per barrel has been preferred for treatment of the various tar fractions.

The catalyst employed may be any of the contact agents generally employed to promote desulfurization. Found especially suitable were oxides of cobalt and 'molybdenum on alumina, molybdenum oxide on alumina, and oxides of nickel and tungsten on alumina.

In accordance with this invention, crude or whole lignite low-temperature tar, yas substantially described in Table l, was distilled to recover phenolic oil and middle oil. Data on this distillation are shown in Table 2 below:

TABLE 2 Distllaton of crude lignite tar PHENOLIC OID Maximum temp., C. 235 Phenolic oil, percent by wt. of feed 27.8 Composition, vol. percent:

Tar bases Y 3.8 'lar acids 22.6 Neutral oil e e 73.6

Hydrocarbon types:

Saturates 9 Oleins Y y l 44 Aromatics 47 Neutral oil characteristics:

Specific gravity, 609/ 60 F. 0.8803 Refractive index 11.2 D 1.4908 Sulfur, percent 1.09 Nitrogen, percent e 0.37

MIDDLE OIL Temp., C. 235-335 Product yield, percent by wt. of feed:

Middle oil e 42.3 Residue 29.9 Middle oil composition, vol. percent:

Tar bases 4.2 Tar acids 1 21.1 Neutildoil b t 74.7

y rocar on ypes:

Satnrates 11 fins 28 Aromatics 43 Middl u Others 18 eo proper es: Specific gravity, 60/60 F. 0.932 Refractive index n2D, 1.5205 Sulfur, percent 0.89 Nitrogen, percent 0.53

Several fractions produced by distillation of lowtemperature lignite ta'r were hydrorefned in `accordance with the present invention. VFeedstock A is a mixture of phenolic and middle oils Which'have been caustic-washed. Feedstock B is a mixture of middle oilA and caustic-washed phenolic oil. Feedstock C is middle oil. Analyses of the feedstocks, data on hydrfnefining-y conditions and analyses of the products of hydroreiiitirigv -aiegg'ivenintbe tables below. 4

TABLE 3 The reformate or hydrorefined product is a partially Feedsfock analysis aromatic oil which may be distilled into several fractions which may be employed as commercial solvents. The Type feedstock n A B C properties of these several fractions indicate good solvent 5 characteristics. by reason of their aromaticity and low speeine gravity, tim/00F 0,8803 0,9252 0,9382 SPIUI am? mtroge? Pqntents Data for vallons ffa' Refractive index, 2 D.. 1. 490s 1.5135 1.5255 tions obtained by distilhng a hydrorened liquid product qlgeggfct jg? g2g; 322g from middle oil and caustic-washed phenolic oil (B in Mixed eniiine pouD o 43.3 49.0 49.5 Tables 3-5) Iare given in Table 6 below. The fractions Dstligttigojg pointlfljnf 15, 99 187 10 boiling above 93 C. were washed with 70% sulfuric 5%----- 17s 170 225 acid. g: g 21,33 ggg Having thus described the invention, I claim: 110%-- 203 242 76 1. In the utilization of low-temperature tars containing ggg gli 33g combined heteroatoms to prepare reined hydrocarbon (72%-.. 247 289 15 liquids suitable as solvents, the method comprising dis- Sggg;jjj jjjjjjjj ggg tlllmg said tars to recover phenolic oil and middle oil; 90% 304 extracting the tar acids from said phenolic oil; and hydroreining a mixture of the oil from which tar acids have TABLE 4 Hydrorefnng conditions a B o Contact agent Co0.MoOi.Ah0| OoO.MoO;.Alz0i MoOLAhO; Temperature, C-- 612 512 493 Pressure, p.s.i.g 500 500 200 Liquid hourly space velocit l. 0 1. 0 0. 67 E, feed, eu. it. per bbl 3,000 3, 000 3. 475

TABLE 5 30 been extracted as aforesaid and said middle oil by catalytic treatment with hydrogen -at a temperature between i r d Reformatep o cts 800 F. and l150 F., a pressure between l100 and 1000 A B C pounds per square inch gauge and a liquid hourly space velocity between 0.25 and 4.0. 35 2. In the utilization of low-temperature tars containing Pfirqgiiiiill.'.ICL 92 ei 88.2 Combined hetervatoms t0 prepare rened hydrocarbon glaegmie 5.7 4.6 04 liquids, the method comprising distilling said tars to re- H, consumed, eu. fr. b1 992 701 1,132 cover phenolic oil and middle oil; extracting the tar acids 1,239 1,662 40 and tar bases from said phenolic oil to leave a neutral organic Product: oil; hydroretining said middle oil and said neutral oil in specific gravity, 00/50 F o. 8577 o. 3535 Reframve memup 1.4962 1 5050 adrruxture by catalytic treatment with hydrogen at a frigeerpegnciI-w 0014 g1g temperature between 800 F. and 1i150F., a pressure Mixed eniiine peint, o 40.0 45. 5 between 100 and 1000 pounds per square inch gauge and a liquid hourly space velocity between 0.25 and 4.0.

TABLE 6 Solvent data Fraction,0 93 93-135 135-279 179-216 21S-288 288-Deeomp. Yield, vol. percent, hydroreilned organic Product 9. 3 s. 9 12. 3 17. 5 30. s 7. 4 specine gravity, e0/5o F.- .587s .7072 .8076 .844s .8959 .9285 Mixed aniiine peint, o- 149. 4 4s. 89 43. 33 42.22 42. 7s 47.22 Sulfur, percent .0 Nil .008 0.016 0.03 0.00 Refractive index, WD 1.4052 1. 431s 1. 4553 1.4772 1. 5131 1.5303

1 Straight aniline point. O.

References Cited in the file of this patent UNITED STATES PATENTS 1,932,186 Pier et a1. Oct. 24, 1933 2,040,100 Miller May 12, 1936 2,620,362 Stiles Dec. 2, 1952 2,755,225 Porter July 17, 1956 2,795,534 Sweeney June 11, 1957 '2,799,678 Sweeney July 16, 1951 

1. IN THE UTILIZATION OF LOW-TEMPERATURE TARS CONTAINING COMBINED HETEROATOMS TO PREPARE REFINED HYDROCARBON LIQUIDS SUITABLE AS SOLVENTS, THE METHOD COMPRISING DISTILLING SAID TARS TO RECOVER PHENOLIC OIL AND MIDDLE OIL, EXTRACTING THE TAR ACIDS FROM SAID PHENOLIC OIL, AND HYDROREFINING A MIXTURE OF THE OIL FROM WHICH TAR ACIDS HAVE BEEN EXTRACTED AS AFORESAID AND SAID MIDDLE OIL BY CATALYTIC TREATMENT WITH HYDROGEN AT A TEMPERATURE BETWEEN 800*F. AND 1150*F., A PRESSURE BETWEEN 100 AND 1000 POUNDS PER SQUARE INCH GAUGE AND A LIQUID HOURLY SPACE VELOCITY BETWEEN 0.25 AND 4.0. 